Head-retract circuit for moving media storage apparatus

Abstract

A moving media storage apparatus including a head actuator driven by flyback emf generated by a spindle motor. The spindle motor is driven by V BAT , whereas the head actuator includes a head-control circuit and an H-bridge MOSFET construction which is driven by V BAT or V CC during normal operation, and a head-retract circuit which is driven by V AUX after a battery failure. A pair of bipolar transistors are provided in the head actuator for increasing the amount of time V AUX is available to drive a head-retract procedure.

We claim: 
     
       1. A moving media storage apparatus comprising: a spindle motor having a first pole;   a spindle driver for generating a spindle motor driving signal, said spindle driver including a first MOSFET having a first drain connected to a power supply, a first source connected to said first pole of said spindle motor, and a first body connected to ground, said first source and said first body not being shorted together;   a voice-coil motor; and   a head actuator for driving said voice-coil motor, said first pole of said spindle motor being connected via a diode to said head actuator.   
     
     
       2. The apparatus according to claim 1 further comprising a capacitor having a first terminal connected to a cathode of said diode. 
     
     
       3. The apparatus according to claim 2 further comprising a zener diode connected in parallel with said capacitor. 
     
     
       4. The apparatus according to claim 1 wherein said first MOSFET is an n-channel MOSFET. 
     
     
       5. The apparatus according to claim 1 further comprising a Schottky diode connected between said power supply and said head actuator. 
     
     
       6. The apparatus according to claim 1, wherein said head actuator comprises a head retract circuit for sensing a reduction in a voltage supplied by said power supply. 
     
     
       7. The apparatus according to claim 1 wherein said spindle driver includes first, second and third MOSFETs and said spindle motor has first, second and third poles, said poles being connected via first, second and third diodes, respectively, to said head actuator. 
     
     
       8. The apparatus of claim 1 wherein said head actuator comprises: a first bipolar transistor connected between a first pole of said voice-coil motor and said diode and a second bipolar transistor connected between a second pole of said voice-coil motor and ground; and   a head-retract circuit, connected to a base of said first bipolar transistor and a base of said second bipolar transistor.   
     
     
       9. The apparatus of claim 8 further comprising: a capacitor having a first terminal connected to a cathode of said diode; and   a grounded zener diode connected in parallel with said capacitor.   
     
     
       10. The apparatus of claim 9 wherein said head actuator further comprises: a head-control circuit.;   a second MOSFET having a second drain connected to said power supply, a second source connected to said first pole of said voice-coil motor, a second body connected to ground, and a second gate connected to said head-control circuit, said second body not being shorted to said second source;   a third MOSFET having a third drain connected to said power supply, a third source connected to said second pole of a voice-coil motor, and a third body connected to said head-control circuit, said third body not being shorted to said third source.   
     
     
       11. The apparatus of claim 10 further comprising a parallel combination of a fourth MOSFET and a diode, said parallel combination being connected between said power supply and said head actuator. 
     
     
       12. A moving media storage apparatus connected to a power supply, said apparatus comprising: a spindle motor;   a voice-coil motor having a first pole and a second pole;   a spindle driver connected to said spindle motor; and   a head actuator comprising:   a head control circuit,   a first MOSFET having a first drain connected to said power supply, a first source connected to said first pole of said voice-coil motor, a first body connected to ground, and a first gate connected to said head control circuit, said first source not being shorted to said first body,   a second MOSFET having a second drain connected to said power supply, a second source connected to said second pole of said voice-coil motor, a second body connected to ground, and a second gate connected to said head control circuit, said second source not being shorted to said second body, and   an auxiliary voltage line, said first pole being connected to said auxiliary voltage line through a first diode, and said second pole being connected to said auxiliary voltage line through a second diode.   
     
     
       13. The apparatus of claim 12 further comprising: a head-retract circuit; and   a push-pull halfbridge comprising: a first bipolar transistor connected between said auxiliary voltage line and said first pole of said voice-coil motor and having a first base connected to said head-retract circuit; and   a second bipolar transistor connected between said second pole of said voice-coil motor and ground and having a second base connected to said head-retract circuit.     
     
     
       14. The apparatus of claim 13 further comprising: a capacitor having a first terminal connected to said auxiliary voltage line and a second terminal connected to ground. 
     
     
       15. The apparatus of claim 14 wherein said spindle motor comprises a third pole, said spindle driver comprises a third MOSFET having a drain connected to said power supply, a third source connected to said third pole, and a third body connected to ground, said third source not being shorted to said third body, said third pole being connected to said auxiliary voltage line through a third diode. 
     
     
       16. The apparatus of claim 14 further comprising a zener diode connected in parallel with said capacitor. 
     
     
       17. The apparatus according to claim 13 wherein the second bipolar transistor is an NPN bipolar transistor and said first bipolar transistor is a PNP bipolar transistor. 
     
     
       18. The apparatus of claim 12 further comprising a parallel combination of a third MOSFET and a third diode, said parallel combination being connected between said power supply and said auxiliary voltage line. 
     
     
       19. The apparatus of claim 18 wherein a body of said third MOSFET is not shorted to a source of said third MOSFET.